Johannes Kepler wrote Astronomia Nova (1609) in a singleminded drive to sweep away the ancient and medieval clutter of spheres and orbs and to establish a new truth in astronomy, based on physical causality. Thus a good part of the book is given over to a nontechnical discussion of how planets can be made to move through space by physical forces. This is the theme of the readings in the present module. The selection includes Kepler's Introduction as well as a selection of chapters that develop the physics of planetary motion. In these ground-breaking chapters, the true Kepler emerges, not as a speculative mystic or a number-crunching drudge, but as a first-rate scientific thinker with a wonderfully engaging narrative style.

This is one of the most important studies in decades on Johannes Kepler, among the towering figures in the history of astronomy. Drawing extensively on Kepler's correspondence and manuscripts, James Voelkel reveals that the strikingly unusual style of Kepler's magnum opus, Astronomia nova (1609), has been traditionally misinterpreted. Kepler laid forth the first two of his three laws of planetary motion in this work. Instead of a straightforward presentation of his results, however, he led readers on a wild goose chase, recounting the many errors and false starts he had experienced. This had long been deemed a ''confessional'' mirror of the daunting technical obstacles Kepler faced. As Voelkel amply demonstrates, it is not. Voelkel argues that Kepler's style can be understood only in the context of the circumstances in which the book was written. Starting with Kepler's earliest writings, he traces the development of the astronomer's ideas of how the planets were moved by a force from the sun and how this could be expressed mathematically. And he shows how Kepler's once broader research program was diverted to a detailed examination of the motion of Mars. Above all, Voelkel shows that Kepler was well aware of the harsh reception his work would receive--both from Tycho Brahe's heirs and from contemporary astronomers; and how this led him to an avowedly rhetorical pseudo-historical presentation of his results. In treating Kepler at last as a figure in time and not as independent of it, this work will be welcomed by historians of science, astronomers, and historians.

Here, Rhonda Martens offers the first extended study of Kepler's philosophical views and shows how those views helped him construct and justify the new astronomy.".

Kepler's Physical Astronomy is an account of Kepler's reformulation of astronomy as a physical science, and of his successful use of (incorrect) physics as a guide in his astronomical discoveries. It presents the only reliable account of the internal logic of Kepler's so-called first and second laws, showing how and to what extent Kepler thought he had derived them from his physical principles. It explains for the first time Kepler's attempt to use an obscure discovery of Tycho Brahe to unify and confirm all of his own physical theories. It also describes the intricate (and neglected) theory which Kepler developed to account for the additional anomalies needed for the theory of the moon.

The brilliant German mathematician Johannes Kepler (1571-1630), one of the founders of modern astronomy, revolutionized the Copernican heliocentric theory of the universe with his three laws of motion: that the planets move not in circular but elliptical orbits, that their speed is greatest when nearest the sun, and that the sun and planets form an integrated system. This volume contains two of his most important works: The Epitome of Copernican Astronomy (books 4 and 5 of which are translated here) is a textbook of Copernican science, remarkable for the prominence given to physical astronomy and for the extension to the Jovian system of the laws recently discovered to regulate the motions of the Planets. Harmonies of the World (book 5 of which is translated here) expounds an elaborate system of celestial harmonies depending on the varying velocities of the planets.

"In 1611, Kepler wrote an essay wondering why snowflakes always had perfect, sixfold symmetry. It's a simple enough question, but one that no one had ever asked before and one that couldn't actually be answered for another three centuries. Still, in trying to work out an answer, Kepler raised some fascinating questions about physics, math, and biology, and now you can watch in wonder as a great scientific genius unleashes the full force of his intellect on a seemingly trivial question, complete with new illustrations and essays to put it all in perspective."—io9, from their list "10 Amazing Science Books That Reveal The Wonders Of The Universe" When snow began to fall while he was walking across the Charles Bridge in Prague late in 1610, the eminent astronomer Johannes Kepler asked himself the following question: Why do snowflakes, when they first fall, and before they are entangled into larger clumps, always come down with six corners and with six radii tufted like feathers? In his effort to answer this charming and never-before-asked question about snowflakes, Kepler delves into the nature of beehives, peapods, pomegranates, five-petaled flowers, the spiral shape of the snail's shell, and the formative power of nature itself. While he did not answer his original question—it remained a mystery for another three hundred years—he did find an occasion for deep and playful thought. "A most suitable book for any and all during the winter and holiday seasons is a reissue of a holiday present by the great mathematician and astronomer Johannes Kepler…Even the endnotes in this wonderful little book are interesting and educationally fun to read."—Jay Pasachoff, The Key Reporter —New English translation by Jacques Bromberg —Latin text on facing pages —An essay, "The Delights of a Roving Mind" by Owen Gingerich —An essay, "On The Six-Cornered Snowflake" by Guillermo Bleichmar —Snowflake illustrations by Capi Corrales Rodriganez —John Frederick Nims' poem "The Six-Cornered Snowflake" —Notes by Jacques Bromberg and Guillermo Bleichmar